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Cell Biology of Disease > Post Translational Modification: Lecture 2 > Flashcards

Post Translational Modification: Lecture 2 Flashcards

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1
Q

What cellular events is PTM involved in? (6)

A

gene expression
signal transduction
cell-cell interaction
protein-protein interaction
communication between intra and extracellular environment

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2
Q

What is trasncriptome?

A

whole mass of mrna transcripts in the body

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3
Q

what is PTM?

A

Covalent addition to or cleavage of proteins
After/ during biosynthesis
important in cell signalling
occurs on amino acid chains or at a terminal

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4
Q

What is proteome?

A

total mass of proteins in body- roughly 1 million

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5
Q

How are there more proteins than genes?

A

splicing process and PTM

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6
Q

what are the 3 types of germ layers that cells can differentiate into?

A

Endoderm- internal layer e.g. lung, thyroid, pancreatic cell
Mesoderm- middle layer e.g. cardiac, rbc, smooth muscle gut, skeletal muscle
Ectoderm- outer layer e.g. skin cells, neurone brain, pigment cells.

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7
Q

how does PTM relate to proteome?

A

PTM increase diversity of proteome whilst extending function and stability- because it affects the longevity as well as activity of protein.

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8
Q

Types of PTM to a protein? (5)

A

Glycosylation
Phosphorylation
Disulfide bond
Methylation
Acetylation

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9
Q

summary of glycosylation?

A

attach sugar- usually to N or O in amino acid side chain

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10
Q

summary of methylation?

A

add methyl group- usually at lysine or arginine residues

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11
Q

summary of acetylation?

A

add acetyl group to N-terminus of protein or at lysine residues

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12
Q

summary of disulfide bond?

A

covalent bond of S at two cysteine residues

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13
Q

summary of phosphorylation?

A

Add phosphate to serine, threonine or tyrosine

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14
Q

genres of PTM? (4)

A

cleavage- proteolysis
complex molecules- glycosylation
chemical- acetylation, methylation, phosphorylation
proteins/peptides- ubiquitylation, sumoylation

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15
Q

example of cleavage PTM in cell?

A

Insulin production. Unwanted parts of the peptide removed after translation and translocation and folding. It gets PMT with disulfide bonds (signal peptide) and then gets exported to Golgi where it’s cleaved

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16
Q

Whats the point of adding functional groups as PMT?

A

enable cell signalling and cell can react specifically and rapidly to events like environmental conditions. Fast bc can just activate/inactivate protein for rapid response e.g. insulin

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17
Q

key points of effects of phosphorylation? (4)

A
  1. Reversible addition/removal
  2. Phosphate from hydrolysis of ATP to ADP
  3. Cause conformational change bc phosphate -2 charge. Cause charge disparity in amino acids and change structure
  4. Can activate (open up/reveal active site) or deactivate (mask binding site)
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18
Q

2 ways phosphate can be added/taken away?

A

protein kinase and phosphatase

19
Q

What does protein kinase do?

A

catalyse transfer of phosphate from high energy donor to specific substrate phosphorylation

20
Q

what is kinome?

A

whole family of 513 kinases- 35 atypical catalytical domain, 478 homologous domain

21
Q

what does phosphatase do and key points about it? (4)

A

catalyses dephosphorylation- removal of phosphate from substrate by hydrolysing monoesters into phosphate ion and molecule with free hydroxyl group
Broad range or specific
broad range controlled by regulatory proteins
often in chain-cell signalling

22
Q

Steps of phosphorylation in regulating glycogen breakdown?

A
  1. epinephrine bind receptor
  2. activates adenylyl cyclase
  3. adenylyl cyclase convert atp to cAMP
  4. cAMP activate cAMP-dependant protein kinase
  5. this activates phosphorylase kinase by phosphorylation
  6. this activates glycogen phosphorylase by phosphorylation
  7. converts glycogen to glucose-1-phosphate
23
Q

What is definition of glycosylation?

A

carbohydrate (monomer to complex) covalently bound to functional group e.g. hydroxyl on protein by glycosidic bond

24
Q

Functions of glycosylation? (6)

A
  1. correct folding
  2. increase protein stability- secreted proteins
  3. cell/cell or cell/environment adhesion
  4. immune response
  5. hormone activity
  6. embryonic development
25
Q

what is the molecule which anchors carbohydrate to the membrane?

A

Dolichol

26
Q

Whats the process of dolichol, glycosylation and golgi?

A

membrane of ER have dolichol with phosphate on the side of cytosol. Then carbs added.
Then flipase flips it so its on the lumen side.
Simultaneously, ribosome translating mrna and folding
Glycosyl transferase attach the carb structure to the polypeptide
Gets transferred to golgi where gets modified- n-linked or o-linked glycosylation

27
Q

what are all the types of places glycosylation can get linked?

A

N-linked
O-linked
C-linked
Glypiation
Phosphoglycosylation

28
Q

Bond, location example of N-linked?

A

Glycan bind to amino group on asparagine
endoplasmic reticulum
insulin receptor, ecm, regulation

29
Q

bond, location, example O -linked?

A

monosaccharides bind to hydroxyl group serine/threonine
ER, golgi, cytosol
collagen, pathogenic bacteria e.g. clostridium toxins

30
Q

Bond, loaction example Glypiation?

A

glycan core links a phospholipid and protein
plasma membrane?
anchors cell surface proteins

31
Q

bond of C-linked?

A

Mannose binds to indole ring of tryptophan

32
Q

Main points of acetylation? (4)

A

addition/removal of acetyl group (CO-CH3)
donated by Ac-CoA
co or post translational
80-90% co translational at N-terminal of polypeptide

33
Q

what are the 2 types of acetylation?

A

N- terminal:
*co-translational modification eukaryotes
*synthesis localisation stability
*80-90% proteins

Lysine acetylation:
*acetylation /deacetylation linked to transcription factors
*activation of gene expression

34
Q

what is NAT and what it do?

A

N-terminal acetyltransferases- catalyses n terminal acetylation
transfer acetyl group from coA to the alpha amino group on the first amino acid residue of polypeptide chain

35
Q

how does histone modification work and what controls it?

A

histone acetylation- controlled by HAT/ KAT (histone/lysine acetyltransferase). Relaxes chromatin structure.
histone deacetylation- controlled by HDAC/KDAC (histone/lysine deacetylase) remove acetyl group and DNA get more tighter, reduce gene expression

36
Q

How does acetylation of histone increase transcription?

A

removes positive charge from the histone, encourage binding of effector proteins and relaxation of chromatin

37
Q

Therapeutic applications of acetylation? (3)

A
  1. targeting HDAC in malignant cells- because these are in charge of reducing gene expression
  2. HDI- small molecule inhibitors
  3. T cell lymphoma targeted by issuberoylinine hydroxamic acids
38
Q

Methylation and key points? (3)

A

addition of methyl group CH2- changes activity of protein
lysine- 3 times methyl can be transferred
arginine- 2 times methyl transferred

39
Q

key points of lysine methylation? (4)

A

activation/suppression
reversed with demethylase
histone function regulation
epigenetic regulation of transcription

40
Q

What is KMT?

A

lysine methyltransferase. Donates the methyl group from S-adenosylmethionine

41
Q

difference between carbonyl and nitrogen methylation?

A

carbonyl- reversible and used to modulate reaction
nitrogen- irreversible and used to create new amino

42
Q

Key points of arginine methylation? (5)

A

regulating RNA processing
gene transcription
DNA damage repair
protein translocation
signal transduction

43
Q

what’s p53 got to do with PMT? (4)

A
  1. p53 activity controlled by acetylation, phosphorylation, methylation
  2. concentrated in N and C terminals
  3. acetylation increase p53 stability- increase dna interaction
  4. under stress, upregulation of kinase activity- reduce p53 activity and increase cofactor activity

Cell Biology of Disease (5 decks)

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